The present invention relates to a method to remedy intake valve sticking in an internal combustion engine. More particularly, this invention relates to a method to remedy intake valve sticking utilizing a hydrocarbyl poly(oxyalkylene) aminocarbamate fuel additive.
It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or "deposit control" additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art.
However, it is also known that some detergent additives which remove carbonaceous engine deposits actually cause valve sticking, especially at low temperatures, when they work their way up the valve stem. See, for example, S. Mikkonen et al., "Intake Valve Sticking In Some Carburetor Engines", SAE Technical Paper Series 881643, Society of Automotive Engineers, Inc. U.S.A., 1988. According to this article, valve sticking did not occur in gasolines containing no detergent additives, but was observed at times when detergent additives were added to the same gasoline.
Poly(oxyalkylene) amines are also well known in the art as fuel additives for the prevention and control of engine deposits. For example, U.S. Pat. No. 4,191,537, issued Mar. 4, 1980 to R. A. Lewis et al., discloses a fuel composition comprising a major portion of hydrocarbons boiling in the gasoline range and from 30 to 2000 ppm of a hydrocarbyl poly(oxyalkylene) aminocarbamate having a molecular weight from about 600 to 10,000, and at least one basic nitrogen atom. The hydrocarbyl poly(oxyalkylene) moiety is composed of oxyalkylene units selected from 2 to 5 carbon oxyalkylene units. These fuel compositions are taught to maintain the cleanliness of intake systems without contributing to combustion chamber deposits.
Similar poly(oxyalkylene) amine fuel additives and fuel compositions containing such additives are described in U.S. Pat. Nos. 4,160,648; 4,236,020; and 4,288,612.
Moreover, U.S. Pat. No. 4,270,930, issued Jun. 2, 1981 to Campbell et al., discloses a fuel composition containing from 0.3 to 3 weight percent of a hydrocarbyl poly(oxyalkylene) aminocarbamate additive for use in keeping combustion chambers clean.